Season of birth and diagnosis of children with leukaemia: an analysis of over 15 000 UK cases occurring from 1953-95

If infections are involved in the aetiology of childhood leukaemia then sea sonal Variation in the birth or onset dates of the malignancy may be appare nt. Previous studies that have examined seasonality of these dates have pro duced conflicting results. Using population-based data from the National Re gistry of Childhood Tumours we conducted a larger study than any to date of 15 835 cases of childhood leukaemia born and diagnosed in the UK between 1 953-95. We found no evidence of seasonality in either month of birth or mon th of diagnosis overall or in any subgroups by age, sex, histology or immun ophenotype. We did however find a significant (P = 0.01) February peak in m onth of birth for cases born before 1960 and a significant (P = 0.02) Augus t peak in month of diagnosis for those diagnosed before 1962. Whilst these findings may be due to chance they are also consistent with changes over ti me in the seasonality of exposure, or immunological response, to a relevant infection. Changes in the seasonal variation in the fatality rate of a pre -leukaemic illness, such as pneumonia, could be another explanation. (C) 20 01 Cancer Research Campaign.